Control means for fluid flow valves

ABSTRACT

Control means for modulating the valve head of a fluid flow delivery valve to maintain substantially a desired flow condition. Pressure of the fluid flow being delivered operates pressure differential means which are arranged to regulate a pressure reducer through which fluid is supplied from upstream of the valve head to a datum pressure chamber. The valve head is responsive to pressure in the datum chamber and thereby is modulated by varying fluid flow delivery.

U United States Patent 1 [111 3,734,12o Rowe et al. 1 May 22, 1973 [54]CONTROL MEANS FOR FLUID FLOW ces C d VALVES UNITED STATES PATENTS [75]Inventors: Charles. Eastqhmnock 1,841,608 1/1932 Kruse ..137/220 nearYeovil, John Richardson 3362424 11968 S l l 722 Bennett, Yeovil, both ofEngland l mlt eta 3 0 g Normalair'Garrett (Holdings) PrimaryExaminerHenry T. Klinlksiek Limited t Somerset England Attorney-RobertsB. Larson et a1. [22] Filed: Nov. 5, 1971 [21] Appl.No.: 195,992 [57]ABSTRACT Control means for modulating the valve head of a [30] ForeignApplicafiun Priority Data fluid flow delivery valve to maintainsubstantially a desired flow condition. Pressure of the fluid flow beingNov. 20, 1970 Great Britain ..55,34 7/70 delivered operates pressuredifferential means which are arranged to regulate a pressure reducerthrough [52] US. Cl ..l37/220 which fluid is supplied from upstream ofthe Valve [51] Int. Cl ..Fl6k 31/12 h dt d t h b Th 1 h 58 Field ofSearch ..137/ll6,3,220 0 a a Pressure c e ea responsive to pressure inthe datum chamber and thereby is modulated by varying fluid flowdelivery.

8 Claims, 1 Drawing Figure v PATENTimYzzm al/ r CONTROL MEANS FOR FLUIDFLOW VALVES This invention relates to fluid flow valves, especially butnot exclusively, pneumatic valves, and has as one objective theprovision of a simple and compact means, preferably incorporating a ratefeature, for so controlling such a fluid flow valve as to maintainsubstantially a desired condition of flow from the valve. A furtherobject is the provision of a fluid flow valve incorporating such controlmeans in a'compact assembly.

In one aspect, therefore, the invention provides for a fluid flow valvehaving a valve head movable to adjust fluid flow through the valve,control means comprising a differential pressure-sensitive mechanismadapted for operative association with the valve head and to beconnected to respond to departure from a selected difference between adatum pressure and the pressure of the valve-controlled fluid downstreamof the valve to cause movement of the valve head in the sense to restoresaid selected pressure difference, said datum pressure being derivedfrom the fluid flow upstream of the valve head via a pressure reducingvalve.

Desirably said reducing valve means are responsive both to changes inthe datum pressure delivered thereby and to the rate of change of suchpressure.

In preferred embodiments, said reducing valve means comprises a firstchamber and a second chamber separated by a common movable wallresponsive to the difference between the fluid pressures in therespective chambers; a pressure reducing valve controlled by theposition of said movable wall and having its discharge connected to saidfirst chamber; a relief valve also controlled by the position of saidmovable wall; and a datum pressure output line connected to said firstchamber and to said relief valve and also, via a restriction, to saidsecond chamber.

The invention also provides a fluid flow valve equipped with the saidcontrol means. Thus, in another aspect, the invention provides a fluidflow valve having a valve head movable to adjust fluid flow through thevalve and control means including a displaceable wall bounding a datumpressure chamber and having its external face exposed to thevalve-controlled fluid downstream of said valve head, said wall beingoperatively connected to said valve head to move the latter invalve-closing direction by displacement of the wall in response torising downstream controlled fluid pressure, and conversely; andpressure reducing valve means for supplying said datum pressure chamberwith controlled fluid from upstream of said valve head at a datumpressure selected in accordance with a required downstream controlledfluid pressure.

In such a valve, the said pressure reducing valve means for supplyingcontrolled fluid to the datum pressure chamber desirably comprise afirst chamber and a second chamber separated by a common movable wallresponsive to the difference between the fluid pressures in therespective chambers; a pressure reducing valve controlled by theposition of said movable wall and having its discharge connected to saidfirst chamber; a relief valve also controlled by the position of saidmovable wall and a datum pressure line connecting said datum pressurechamber to said first chamber and to said relief valve and also, via arestriction, to said second chamber.

Preferably the valve head is a pressure-balanced axially movable membersupported by an inner valve housing accommodating a datum pressurechamber.

The invention will now be described by way of exam ple with reference tothe accompanying drawing, which schematically illustrates an in-linepressure regulating valve equipped with control means according to theinvention.

An in-line valve is one in which the valve head moves axially insubstantial alignment with the fluid flowing through it. In theillustrated valve, part of the control means is housed in an innerhousing within the valve and part, namely a pressure reducing and reliefvalve assembly 10, is external.

The assembly 10 comprises a substantially cylindrical body 11 containingthree axially disposed chambers, namely, a first outer chamber 12, acentral chamber 13 and a second outer chamber 14. The central chamber 13is separated from the first and second outer chambers 12, 14, byflexible rolling diaphragms 15, 16, re spectively. On the axial centerline of the body 11 at the outboard side of the first outer chamber 12is provided a pressure reducing valve 17, whilst similarly positioned onthe outboard side of the second outer chamber 14 is a relief valve 18. Apush-rod 19 is sealed to and supported by the diaphragms 15, 16, in amanner such that it can move axially and actuate the two valves 17, 18.The push-rod 19 is biased towards opening the pressure reducing valve 17by a compression spring 20 housed in second outer chamber 14. Adjustmentof the reducing valve is provided by means of a rate adjuster (notshown) associated with spring 20. An outlet 21 from first outer chamber12 connects with a manifold conduit 22 which communicates with ambientby way of the relief valve 18 and second outer chamber 14 which isprovided with a vent connection 23; it also connects with centralchamber 13 by way of an orifice 24. The manifold conduit 22 alsoprovides for connection with a datum pressure chamber 40 of the in-linevalve 30. An inlet 25 to the reducing valve 17 provides connection witha region of the valve 30 upstream of the valve head thereof.

The in-line valve 30 comprises a substantially tubular casing 31supporting coaxially with its interior a body 32 providing a housing fora valve assembly 33. The valve assembly 33 comprises a valve head 34projecting from the upstream end of the body 32 and secured by a spindle35 to a piston 36 operating in a chamber 37 at the downstream end of thebody 32. The wall of the chamber 37 is provided with holes 38, whichenables the face of the piston 36 to sense pressure downstream of thevalve head 34. The piston 36 makes a sliding seal within the chamber 37by means of a piston ring type seal 39, whereby the chamber 37 isdivided to create a datum pressure chamber 40 at the back of the piston36. Conduit connection to the datum pressure chamber is by way of a duct41 through a web supporting the body 32 within the casing 31, andconnects with the manifold conduit 22 of the control means 10. The valvespindle 35 slides in front and rear bearings 42, 43, carried in abearing housing 44 of the body 32. Between the bearings 42, 43, is aseal 45 and a grooved and ported collar 46. The collar 46 :is positionedbetween the front bearing 42 and the seal 45. The collar 46 is alignedwith a portway 47 communicating with the outside of the body 32, wherebyfluid seeping past the front bearing may escape which, together with theseal 45, substantially prevents seepage into the datum pressure chamber40. The upstream end of the body 32 provides a shroud 48 into which thevalve head 34 moves when opening. The valve head 34 is in the form of askirted piston and has the upstream edge of the skirt scalloped in amanner such that, when the valve head 34 is fully forward, i.e., closingthe valve, the scallops 49 are completely shielded by the walls of theentry duct 50 of the casing 31. The scallops 49 are shaped so that, asthe valve head 34 initially moves towards the open position or movesfinally towards the closed position, the area of the flow passage variesat a rate that is more gradual than when the edge of the valve head 34is moving within the region of increasing diameter of the casing 31. Toensure pressure balance across the valve head 34 at least one hole 51 isprovided therethrough, being screened by a coned shield 52. The smallannular clearance between the upstream edge of the skirt of the valvehead 34 and the entry duct 50 and the similar clearance between thedownstream edge of the skirt of the valve head and the shroud 48 isprotected from dirt in the fluid flow by an annular shield 53 pressedinto the entry 50. A pressure tapping connection 54 communicates withthe annular region in the entry formed by the shield 53 and connectswith the pressure reducing valve 17 of the control means 10. A lightspring (not shown) moves the piston assembly 33 to the closed positionwhen the valve 30 is inoperative.

In operation of the invention according to the embodiment hereinbeforedescribed the control means obtains a high pressure fluid supply fromthe in-line valve 30 by way of connection 54 and inlet 25 of thepressure reducing valve 17, whilst control pressure is conveyed to thedatum pressure chamber 40 by way of the manifold conduit 22 and duct 41.When the valve 30 is providing the required downstream pressure and thevalve assembly 33 is stationary the pressure in first outer chamber 12,central chamber 13, the manifold conduit 22 and the datum pressurechamber 40 is static, and under such conditions the pressure in thecontrol means is such that the diaphragm has no pressure differentialacross it, and in consequence the pressure reducing valve 17 is heldopen to a predetermined position by influence only of the spring 20.When pressure downstream of the valve head 34 falls, it also obtains inthe piston chamber 37 by way of the holes 38, and causes a pressuredifferential across the piston 36 which tends to move to the right inthe drawing. Due to the reduced pressure in datum pressure chamber 40,conduit manifold 22 and the first outer chamber 12, and due torestriction 24, a pressure differential is created across the diaphragm15 (the greater pressure being in the central chamber 13), whereby thepush-rod 19 is moved to open further the reducing valve 17, so that thepressure rebuilds in first outer chamber 12, conduit manifold 22, anddatum pressure chamber 40, which resets the pressure reducing valve 17to be again influenced only by the spring 20, and so causes the piston36 to return to the left which also returns the valve head to anappropriate regulating position.

When the downstream pressure in the valve 30 rises above the requiredpressure the valve assembly 33 moves to the left in the drawing andincreases the control pressure in the datum pressure chamber 40, conduitmanifold 22 and first outer chamber 12; such action causes the effect ofthe spring 20 to be reduced by the increased pressure applied todiaphragm 15, so that the push-rod 19 is moved to cause the pressurereducer 17 to close accordingly and establish an appropriate pressure inthe datum pressure chamber 40. In the control means 10 pressure variesin the central chamber 13 at a slower rate than in the first outerchamber 12, and the manifold conduit 22, due to the orifice 24; thus theeffect of differential pressure on the diaphragm reduces as the pressurein the central chamber 13 changes towards equalling that in the firstouter chamber.

It will be observed that, using control means as described herein, therate of response of the valve assembly 33 varies with the rate of changeof the downstream pressure. When a change of downstream pressure issmall and slow the resulting pressure difference across the diaphragm 15also is small, due to there being little flow requiring to pass throughthe orifice 24 with con sequently little throttling effect upon thatflow, thereby causing slight movement of the valve assembly 33. However,in circumstances of a sudden and large change of downstream pressure theresulting pressure difference across the diaphragm also is large andquickly obtained due to the considerable throttling effect of theorifice 24 upon the flow therethrough; such conditions cause rapidmovement of the valve assembly 33 which overshoots the position at whichit would be in balance to correct the downstream pressure change.Overshoot movement of a valve assembly whilst speeding attainment of thedesired correction usually introduces a tendency for the valve assemblyto hunt. This control means eliminates any significant hunting because,as the differential pressure across the diaphragm reduces duringcontinuance of flow through the orifice 24, effect upon the valveassembly 33 also reduces, thus the urge for the valve assembly 33 toovershoot is diminished, and it returns to the position of balance andthence to the control position, to substantially maintain the desireddownstream pressure.

It is to be understood that arrangements alternative to the embodimentherein described and illustrated may be provided without departing fromthe scope of the present invention, for example, the diaphragms of thecontrol means may-be substituted by pistons.

We claim as our invention:

1. In a fluid flow valve having a valve head movable to adjust fluidflow through the valve, control means comprising a differential pressuresensitive mechanism for operably regulating the valve head, a datumpressure chamber, a duct connecting fluid flow upstream of the valvehead with said datum pressure chamber, said mechanism including apressure reducing valve for regulating pressure of fluid in said duct, amovable surface defining one wall of said datum pressure chamber, meansexposing said wall-defining movable surface to pressure of fluiddownstream of the valve head, means operably interconnecting the valvehead and the movable surface, said pressure reducing valve having avalve actuating member, and means exposing said valve actuating memberon two opposed surfaces to pressure of fluid in the duct downstream ofthe reducing valve, exposure of one surface being by way of restrictedfluid connection to the duct and of the other surface being by way ofunrestricted fluid connection to the duct.

2. Control means as claimed in claim 1, wherein the valve actuatingmember of the reducing valve is operably connected to a pressure reliefvalve arranged to relieve pressure from the duct.

3. Control means as claimed in claim 2, wherein the valve actuatingmember of the reducing valve provides a common movable wall separating afirst and a second chamber, the discharge of the reducing valve beingconnected to the first chamber so forming part of the duct, and thesecond chamber being connected to the duct by way of the restrictedfluid connection.

4. Control means as claimed in claim 3, wherein the valve actuatingmember of the reducing valve provides a common movable wall separatingthe second chamber and a discharge chamber of the relief valve, thevalve actuating member further providing a push rod secured to the twocommon movable walls and operably connected to the reducing valve at oneend and to the relief valve at the other end.

5. In a fluid flow valve having a valve head movable to adjust fluidflow through the valve, control means comprising a differentialpressure-sensitive mechanism for operably regulating the valve head, adatum pressure chamber, said mechanism including a pressure reducingvalve for regulating pressure of fluid in a duct connecting fluid flowupstream of the valve head with said datum pressure chamber, a pistondefining one wall of the datum pressure chamber being exposed topressure of fluid downstream of the valve head, the valve head and thepiston being operably interconnected, a valve actuating member of thepressure reducing valve being exposed on both sides to pressure of fluidin the duct downstream of the reducing valve, exposure of one side beingby way of restricted fluid connection to the duct and of the other sidebeing by way of unrestricted fluid connection to the duct.

6. Control means as claimed in claim 5, wherein the valve head andpiston are supported for axial move ment in an inner housing disposedconcentrically in the body of the fluid flow valve, and the axialmovement of the valve head providing variable closure with a cooperatingannulus disposed so as to regulate flow past the inner housing.

7. Control means as claimed in claim 6, wherein the valve head is ofannular shape being supported by a perforate web from a shaft extendingfrom the piston.

8. Control means as claimed in claim 7, wherein the upstream edge of thevalve head is notched, and the annulus is coaxial with the valve head,determining by their axial relationship the area available to fluidflow.

1. In a fluid flow valve having a valve head movable to adjust fluidflow through the valve, control means comprising a differential pressuresensitive mechanism for operably regulating the valve head, a datumpressure chamber, a duct connecting fluid flow upstream of the valvehead with said datum pressure chamber, said mechanism including apressure reducing valve for regulating pressure of fluid in said duct, amovable surface defining one wall of said datum pressure chamber, meansexposing said walldefining movable surface to pressure of fluiddownstream of the valve head, means operably interconnecting the valvehead and the movable surface, said pressure reducing valve having avalve actuating member, and means exposing said valve actuating memberon two opposed surfaces to pressure of fluid in the duct downstream ofthe reducing valve, exposure of one surface being by way of restrictedfluid connection to the duct and of the other surface being by way ofunrestricted fluid connection to the duct.
 2. Control means as claimedin claim 1, wherein the valve actuating member of the reducing valve isoperably connected to a pressure relief valve arranged to relievepressure from the duct.
 3. Control means as claimed in claim 2, whereinthe valve actuating member of the reducing valve provides a commonmovable wall separating a first and a second chamber, the discharge ofthe reducing valve being connected to the first chamber so forming partof the duct, and the second chamber being connected to the duct by wayof the restricted fluid connection.
 4. Control means as claimed in claim3, wherein the valve actuating member of the reducing valve provides acommon movable wall separating the second chamber and a dischargechamber of the relief valve, the valve actuating member furtherproviding a push rod secured to the two common movable walls andoperably connected to the reducing valve at one end and to the reliefvalve at the other end.
 5. In a fluid flow valve having a valve headmovable to adjust fluid flow through the valve, control means comprisinga differential pressure-sensitive mechanism for operably regulating thevalve head, a datum pressure chamber, said mechanism including apressure reducing valve for regulating pressure of fluid in a ductconnecting fluid flow upstream of the valve head with said datumpressure chamber, a piston defining one wall of the datum pressurechamber being exposed to pressure of fluid downstream of the valve head,the valve head and the piston being operably interconnected, a valveactuating member of the pressure reducing valve being exposed on bothsides to pressure of fluid in the duct downstream of the reducing valve,exposure of one side being by way of restricted fluid connection to theduct and of the other side being by way of unrestricted fluid connectionto the duct.
 6. Control means as claimed in claim 5, wherein the valvehead and piston are supported for axial movement in an inner housingdisposed concentrically in the body of the fluid flow valve, and theaxial movement of the valve head providing variable closure with acooperating annulus disposed so as to regulate flow past the innerhousing.
 7. Control means as claimed in claim 6, wherein the valve headis of annular shape being supported by a perforate web from a shaftextending from the piston.
 8. Control means as claimed in claim 7,wherein the upstream edge of the valve head is notched, and the annulusis coaxial with the valve head, determining by their axial relationshipthe area available to fluid flow.